1. Field of the Invention
The present invention relates to the use of alpha-(p-alkoxybenzylidene) carboxylic acids of the formula: ##STR1## wherein R is alkoxy of 1 to 20 carbon atoms, R' is hydrogen or alkoxy of 1 to 20 carbon atoms, or R and R' taken together form 3,4-methylene dioxy, R" is hydrogen or alkyl of 1-20 carbon atoms, and R"' is hydrogen or an alkali metal, e.g., sodium or potassium, as color stabilizers, process aids and whiteners for soaps. The invention includes, within its scope, the resulting soap containing at least one compound according to formula I, hereinafter alternatively denoted Compound I.
2. Description of the Related Art
Human skin is generally cleansed with detergents, water, solvents or abrasives, singly or in combination. Among the detergents, soaps have probably enjoyed the widest use. Generally, toilet and household soaps are made by the vacuum chilling/extrusion process of a blend of about 15-25% lauric oil (coconut or palm kernel) and 75-85% hard fat, usually tallow or palm oil. See, for example, Edgar Woollatt "The Manufacture Of Soaps, Other Detergents And Glyceerine," Halsted Press, a division of John Wiley and Sons, New York, N.Y. 1985, 152 et seq.
The most common soap is manufactured by the saponification of a mixture of beef tallow and coconut oil at a ratio of about 80 parts tallow to 20 parts coconut oil. See, for example, chapter 9 of "Soap Technology For The 1990's", Luis Spitz, Ed., American Oil Chemist's Society--Monographer, Champaign, Illinois, 1990. The finished soap is packaged and marketed in a variety of shapes or forms. In order to keep the original overall appearance, odor, quality and performance characteristics, a variety of compounds have been used as preservatives. Most of these preservatives fall under the category of metal sequestrants and antioxidants. According to Whalley, in "Soaps/Cosmetics/Chemical Specialties," 1990:28, these include, for example:
EDTA (Ethylenediamine tetraacetic acid), sodium salt; PA0 HEDP (1-Hydroxyethane-1, 1-diphosphonic acid), sodium salt; PA0 DTPA (Diethylenetriamine pentaacetic acid), sodium salt; PA0 HOEDTA (Hydroxyethenediamine triacetic acid), sodium salt; PA0 NTA (Nitrillo triacetic acid), sodium salt; PA0 Citric Acid (and sodium salt); PA0 Phosphoric Acid (and sodium salt); PA0 Stannous Chloride; PA0 O-Tolyl Biguanide; PA0 Magnesium Silicate; and PA0 BHT (Butylated Hydroxytoluene).
ACS abstract RES. Discl. 213, 471-472 (1982) discloses the use of cinnamic acid in conjunction with glucose to help prevent discolorations of phenolic compounds in certain antibacterial soaps.